Question

Describe how the body maintains acid-base equilibrium.

a. What mechanisms are used? Are these fast or slow responses?

b. How does each of these mechanisms contribute to acid-base balance? (i.e. what does it regulate and how?)

c. How does each of these mechanisms compensate for acidosis? For alkalosis?

Answer 1

a) acid base balance in human body is maintained through acid base homeostasis. The three systems that make acid base balance in our body are : buffer system(quick response), respiratory regulation (quick response) and renal regulation (slow regulation)  of acid base homeostasis.

b) buffer system : the ions present in ohr body acts to bind to H+ ions when the blood becomes more acidic or dissociates to release H+ ions when the blood becomes more alkaline. The three buffer system in pur body are protein buffer system, phosphate buffer system and carbonic acid bicarbonate buffer system.
The buffer systems respond quickly to change in blood ph.
- respiratory system : the lungs help maintain acid bass balance by increasing or decreasing CO2 levels in body. When the blood ph drops, chemoreceptors gets activated and cause firing of action potential to the respiratory centre in midbrain. The respiratory centre sends motor signals to the respiratory muscles to increases rate and depth of respiration. This help increase CO2 removal from body. The CO2 binds with water to form carbonic acid in blood which rapidly dissociates into H+ and HCO3-. Removal of CO2 will help prevent acid formation and release H+ in blood thus reducing the blood ph.
Similarly when blood ph increases, the chemoreceptors sends sensory impulses to the midbrain which suppresses the respiratory centre. Respiratory centre sends motor signals to respiratory muscles to decrease rate of respiration. This increases CO2 in blood causing more carbonic acid formation and H+ in blood. Thus increasing the blood ph.
- renal system : the kidneys sense the change in blood ph and increase H+ excretion in urine when the blood ph drops and increases H+ reabsorption and HCO3- excretion when the blood ph increases.
The response of renal system to maintain acid base balance is a slow response.
c) acidosis is the increased level of H+ ions in blood resulting in acidic blood. The ph drops in acidosis. During acidosis the blood ph drops. The chemoreceptors gets activated and cause firing of action potential to the respiratory centre in midbrain. The respiratory centre sends motor signals to the respiratory muscles to increases rate and depth of respiration. This help increase CO2 removal from body. This helps in bringing the blood ph back to normal.
The kidney also senses rise in H+ ions in blood. The renal tubules increase excretion of H+ in urine. This helps the blood ph to rise.
Alkalosis is the increase in blood ph due to increase in HCO3- concentration in blood. The blood becomes alkaline. when blood ph increases, the chemoreceptors sends sensory impulses to the midbrain which suppresses the respiratory centre. Respiratory centre sends motor signals to respiratory muscles to decrease rate of respiration. This increases CO2 in blood causing more carbonic acid formation and H+ in blood.
The kidney senses the increase in blood ph and causes increased reabsorption of H+ ions and excretion of HCO3- into the urine. This hrlps decrease the blpod ph back to no